Alan Milburn, the former cabinet minister, is to join the growing exodus of senior politicians from parliament by standing down at the next election.

The Darlington MP had emerged virtually unscathed from the expenses scandal, but is likely to face criticism this week when new details of MPs' outside earnings are published: he has five paid roles in addition to his parliamentary work, including posts with PepsiCo and Lloyds Pharmacy.

The 51-year-old former health secretary, best known for quitting the cabinet at the height of his career to spend more time with his partner and two sons, said in a statement yesterday that he wanted to pursue "other challenges". He insisted he had been considering the decision for a long time, adding: "I left frontline ministerial politics, and have not wished to return, because I wanted to have a different way of life. I have never regretted doing so. Standing down as an MP will give me the chance to balance my work and my family life with the time to pursue challenges other than politics."

Milburn, once one of Tony Blair's closest allies, said he was announcing the decision now so that his local party had time to choose a new candidate. But the timing just before the disclosure on 1 July of new details about MPs' outside salaries - and the threat of a ban on outside jobs, which the review of MPs' pay led by Sir Christopher Kelly has been asked to consider - will trigger speculation he was also unwilling to give up his outside interests .

Several MPs have predicted a mass exodus if outside jobs are banned, but Labour MPs are particularly likely to be affected as they are more likely to be in opposition after the next election - leaving current government members with a shortfall in salary to make up, and backbenchers with more time on their hands.

• David Maclean, one of the architects of MPs' fight against disclosure of expenses, is to stand down at the next election. The former Tory chief whip, who has multiple sclerosis, said he could no longer carry out his job at "full pelt". He added: "I said when I was diagnosed with MS that when it began to seriously affect the way I carried out my work, I would step down. That time has arrived."